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Zircon Geochronological Evidence for Participation of the North China Craton in the Protolith of Migmatite of the North Dabie Terrane

2018
Vol.29
No.1

Haijin Xu, Junfeng Zhang

State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China

The plate affiliation of the North Dabie terrane (NDT) has been controversial. To address this fundamental question, an integrated study of internal structure, in-situ U-Pb dating and trace element analysis in zircons and field investigation for migmatite in the NDT was carried out, which reveals participation of crustal rocks of the North China craton (NCC) in the protolith in addition to the more common crustal rocks of the Yangtze craton (YC). The evidence of an NCC affinity for protolith of migmatite in the NDT is the ~2.5 Ga (2 486±14 and 2 406±26 Ma) magamtic age and ~1.8 Ga (1 717±79 Ma) metamorphic age in the relict zircon domains because these two age groups are characteristic for the evolution of the NCC. The evidence of a YC affinity for protolith of migmatite in the NDT is the more common 0.7–0.8 Ga (e.g., 787±12 Ma) magamtic zircon age. Mid-Neoproterozoic magmatic age (0.7–0.8 Ga) is a symbol of YC basement rocks. In view of the widely exposed YC crustal components in the NDT, we suggest that the protolith of the NDT is mainly crustal rocks from the YC with minor crustal components from the NCC. The zircon rim domains and new growth grains from all the migmatite samples are characterized by anatectic zircons and have a widely concordant ages ranging from 112.2±2.8 to 159.6±4.3 Ma with several peak values, suggesting a long lasting multistage anatexis. In conclusion, the NDT has a mixed protolith origin of both the YC and the NCC crustal rocks were strongly remoulded by anatexis during orogenic collapse.